AbstractFire detection using satellites is an important source of information for fire management, ecological studies and emission estimates. However, little is known about the minimum sizes of fires that are being detected. This paper presents an approach using fire radiative power estimated from MODIS satellite data to determine the detection threshold for fire-prone savannas in Northern Australia. The results indicate that fires with an active flaming area 100-300 m(2) can be detected in the study region. It is also shown that the algorithm is slightly more sensitive at night. As expected the detection threshold shows strong view angle dependence. While this study has been undertaken in the savannas of Northern Australia, the results should be transferable to other savanna regions worldwide and other areas where fires are not obscured by a dense tree canopy. (C) 2012 International Society for Photogrammetry and Remote Sensing, Inc. (ISPRS) Published by Elsevier B.V. All rights reserved.